CollapseButton: Added hovering highlight + minor consistency tweaks.

CHANGELOG.txt

@@ -47,6 +47,7 @@ Other Changes:
  - Nav: Added a CTRL+TAB window list and changed the highlight system accordingly. This is designed to allow CTRL+TAB between Tabs in the future. (#787)
  - Window: Allow menu and popups windows from ignoring the style.WindowMinSize values so short menus/popups are not padded. (#1909)
  - Window: Added global io.OptResizeWindowsFromEdges option to enable resizing windows from their edges and from the lower-left corner. (#1495)
+ - Window: Collapse button shows hovering highlight + clicking and dragging on it allows to drag the window as well. 
  - Drag and Drop: Fixed an incorrect assert when dropping a source that is submitted after the target (bug introduced with 1.62 changes 
    related to the addition of IsItemDeactivated()). (#1875, #143)
  - Drag and Drop: Fixed ImGuiDragDropFlags_SourceNoDisableHover to affect hovering state prior to calling IsItemHovered() + fixed description. (#143)

imgui.cpp

@@ -6686,7 +6686,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
             // Collapse button
             if (!(flags & ImGuiWindowFlags_NoCollapse))
-                if (CollapseButton(window->GetID("#COLLAPSE"), window->Pos + style.FramePadding))
+                if (CollapseButton(window->GetID("#COLLAPSE"), window->Pos))
                     window->CollapseToggleWanted = true; // Defer collapsing to next frame as we are too far in the Begin() function
 
             // Close button
@@ -8367,17 +8367,21 @@ bool ImGui::CollapseButton(ImGuiID id, const ImVec2& pos)
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
 
-    ImRect bb(pos, pos + ImVec2(g.FontSize, g.FontSize));
+    ImRect bb(pos, pos + ImVec2(g.FontSize, g.FontSize) + g.Style.FramePadding * 2.0f);
     ItemAdd(bb, id);
-    bool ret = ButtonBehavior(bb, id, NULL, NULL, ImGuiButtonFlags_None);
-    RenderNavHighlight(bb, id);
-    RenderArrow(bb.Min, window->Collapsed ? ImGuiDir_Right : ImGuiDir_Down, 1.0f);
+    bool hovered, held;
+    bool pressed = ButtonBehavior(bb, id, &hovered, &held, ImGuiButtonFlags_None);
+
+    ImU32 col = GetColorU32((held && hovered) ? ImGuiCol_ButtonActive : hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button);
+    if (hovered || held)
+        window->DrawList->AddCircleFilled(bb.GetCenter() + ImVec2(0.0f, -0.5f), g.FontSize * 0.5f + 1.0f, col, 9);
+    RenderArrow(bb.Min + g.Style.FramePadding, window->Collapsed ? ImGuiDir_Right : ImGuiDir_Down, 1.0f);
 
     // Switch to moving the window after mouse is moved beyond the initial drag threshold
     if (IsItemActive() && IsMouseDragging())
         StartMouseMovingWindow(window);
 
-    return ret;
+    return pressed;
 }
 
 void ImGui::Image(ImTextureID user_texture_id, const ImVec2& size, const ImVec2& uv0, const ImVec2& uv1, const ImVec4& tint_col, const ImVec4& border_col)
@@ -8769,9 +8773,10 @@ bool ImGui::CollapsingHeader(const char* label, bool* p_open, ImGuiTreeNodeFlags
     {
         // Create a small overlapping close button // FIXME: We can evolve this into user accessible helpers to add extra buttons on title bars, headers, etc.
         ImGuiContext& g = *GImGui;
-        float button_sz = g.FontSize * 0.5f;
         ImGuiItemHoveredDataBackup last_item_backup;
-        if (CloseButton(window->GetID((void*)(intptr_t)(id+1)), ImVec2(ImMin(window->DC.LastItemRect.Max.x, window->ClipRect.Max.x) - g.Style.FramePadding.x - button_sz, window->DC.LastItemRect.Min.y + g.Style.FramePadding.y + button_sz), button_sz))
+        float button_radius = g.FontSize * 0.5f;
+        ImVec2 button_center = ImVec2(ImMin(window->DC.LastItemRect.Max.x, window->ClipRect.Max.x) - g.Style.FramePadding.x - button_radius, window->DC.LastItemRect.GetCenter().y);
+        if (CloseButton(window->GetID((void*)(intptr_t)(id+1)), button_center, button_radius))
             *p_open = false;
         last_item_backup.Restore();
     }